The present invention relates generally to fluid seals for fuel injectors, and more particularly to a plunger seal designed to compensate for seal wear produced due to the continual reciprocation of the plunger within a barrel.
In one class of fuel injectors, low pressure actuation fluid, such as engine oil for example, forces a piston downward, thereby forcing a plunger to compress and expel high pressure fuel through a nozzle assembly. A spring returns the plunger through the barrel to its starting position, and the cycle begins again. Heretofore, O-rings located around an annulus or groove of the plunger were typically used to prevent the high pressure fuel within the nozzle assembly from mixing with and being diluted by the low pressure oil or other actuation fluid. For example, commonly-owned U.S. Pat. No. 5,901,686 to Stockner et al. teaches a fuel injector having a plunger slidably mounted within a plunger bore, wherein an O-ring within a groove of the plunger prevents fuel from bypassing the plunger within the bore.
Unfortunately, due to the continual reciprocation of the plunger within the barrel of injector, the O-rings would begin to wear. This would eventually lead to seepage of the fuel from the barrel, resulting in the dilution of the high pressure fuel.
The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.
In one aspect of this invention, a pumping assembly for a unit fuel injector comprises a barrel having a bore therein, the bore having a bore surface. A plunger reciprocates within the barrel and has a groove therein. A sealing member is disposed within the groove and has a deformable member. Pressurized fluids within the barrel force the deformable member of the sealing member into sealing contact with the bore surface.
In another aspect of this invention, a plunger assembly is disclosed for use in a fuel injector having a plunger-and-barrel pumping assembly in which a plunger is reciprocated within a bore in a barrel to pressurize fuel to be injected. The plunger assembly comprises a plunger having a groove therein and a sealing member disposed within the groove. The sealing member has a deformable extension adapted to contact a bore surface of a fuel injector barrel.
In still another aspect of this invention, a sealing member adapted to fit within a groove of a fuel injector plunger is disclosed. The sealing member comprises a cylindrical body having a deformable extension extending radially outwardly from the cylindrical body. The extension is configured to sealingly engage a bore surface of a fuel injector barrel and has a surface exposed to pressurized fluid within the barrel to thereby force the deformable extension against bore surface.